Systems and Methods for Purifying Solvents

ABSTRACT

The present disclosure is directed to methods and systems of purifying solvents. The purified solvents can be used for cleaning a semiconductor substrate in a multistep semiconductor manufacturing process.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to U.S. Provisional ApplicationSer. No. 63/000,747, filed on Mar. 27, 2020, the contents of which arehereby incorporated by reference in their entirety.

FIELD OF THE DISCLOSURE

The present disclosure relates to systems and methods for purifyingsolvents (e.g., organic solvents). In particular, the present disclosurerelates to systems and methods that can be used to obtain organicsolvents having a very low amount of organic and metal impurities.

BACKGROUND OF THE DISCLOSURE

The semiconductor industry has achieved rapid improvements inintegration density of electronic components, which are arisen fromcontinuous reductions in the component size. Ultimately, more of thesmaller components are afforded to be integrated into a given area.These improvements are mostly due to the development of new precisionand high resolution processing techniques.

During the manufacturing of high resolution integrated circuits (ICs),various processing liquids will come into contact with a bare wafer or afilm-coated wafer. For zo example, the fabrication of a fine metalinterconnection typically involves a procedure of coating a basematerial with a pre-wetting liquid before the base material is coatedwith a composite liquid to form a resist film. These processing liquids,containing proprietary ingredients and various additives, are known tobe a source of contamination of IC wafer.

It is believed that even if a trace amount of contaminants is mixed intothese chemical liquids, such as a wafer pre-wetting liquid or adeveloper solution, the resulting circuit patterns may have defects. Forexample, it is known that the presence of very low levels of metalimpurities may interfere with the performance and stability ofsemiconductor devices. Depending on the kind of metallic contaminants,oxide property can deteriorate, inaccurate patterns can be formed,electrical performance of semiconductor circuits can be impaired, whicheventually adversely impact manufacturing yields.

The contamination of impurities, such as metal impurities, fineparticles, organic impurities, moisture, and the like, can beinadvertently introduced in a chemical liquid during various stages ofthe manufacturing of the chemical liquid. Examples include impuritiesthat are presented in a raw material, a by-product generated or anunreacted reactant remained when the chemical liquid is manufactured, orforeign matters eluded or extracted from the surface of themanufacturing apparatus or from a container equipment, reaction vessels,or the like used in transporting, storing or reacting. Hence, is areduction or removal of insoluble and soluble contaminants from thesechemical liquids used for the production of highly precise andultra-fine semiconductor electronic circuits is a basic assurance ofproducing defective-free ICs.

In this respect, it is imperative to significantly improve and torigorously control the standard and quality of chemical liquidmanufacturing processes and systems in order to form high puritychemical liquids, which are indispensable in the fabrication ofultra-fine and immensely precise semiconductor electronic circuits.

SUMMARY OF THE DISCLOSURE

Accordingly, to form highly precise integrated circuits, the demands forultra-pure chemical liquids, and the quality improvement and control oftheses liquids become very critical. Specific key parameters targetedfor quality improvement and control include: liquid and on-wafer metalreduction, liquid and on-wafer particle count reduction, on-wafer defectreduction, and organic contaminant reduction.

In view of the above, the present disclosure provides a purificationsystem and a method of purifying a solvent (e.g., an organic solvent)using the same for preparing a solvent targeted for semiconductormanufacturing, in which an ultra-pure solvent is produced with theamounts of metallic impurities, organic impurities, and residualmoisture in the solvent managed within predetermined ranges and withoutthe generation or introduction of unknown and unwanted substances.Hence, the occurrence of residue and/or particle defects is suppressedand the yield of semiconductor wafer is improved. In addition, theinventors found unexpectedly that purifying an organic solvent usingboth dehydration (e.g., by using a molecular sieve column) andfiltration (e.g., by using a filter having a certain pore size) beforesolvent distillation can result in a purified organic solvent having avery low amount of organic impurities (e.g., at least about 99.99%)and/or a very low moisture content (e.g., at most about 100 ppm).Further, the inventors found unexpectedly that purifying an organicsolvent using two different types of negatively charged ion exchangefilters (e.g., one capable of removing heavy metals such as Fe, Ni, Cr,Zn, or Cu and one capable of removing alkali or alkaline earth metalssuch as K, Na, or Ca) after solvent distillation can result in apurified organic solvent having a surprisingly low total amount of metalimpurities (e.g., at most about 200 ppt).

In one aspect, the disclosure features a method of purifying an organicsolvent that includes (1) passing the organic solvent through at leastone column containing an adsorbent to remove water in the organicsolvent, (2) passing the organic solvent through a first filter unit, inwhich the first filter unit includes a first housing and at least onefirst filter in the first housing, and the at least one first filterincludes a filtration medium; and (3) distilling the organic solvent ina distillation column to obtain a purified organic solvent. The firstfilter unit is between the distillation column and the at least onecolumn containing the adsorbent.

In another aspect, the disclosure features a system that includes (1) atleast one column containing an adsorbent, (2) a first filter unitdownstream of and in fluid communication with the at least one columncontaining an adsorbent, in which the first filter unit includes a firsthousing and at least one first filter in the first housing, and thefirst filter includes a filtration medium; and (3) a distillation columndownstream of and in fluid communication with the first filter unit.

In another aspect, the disclosure features a method of purifying anorganic solvent that includes (1) distilling the organic solvent in adistillation column to obtain a distilled organic solvent; and (2)passing the distilled organic solvent through an ion exchange filterunit to obtain a purified organic solvent. The ion exchange filter unitincludes a housing and at least one first ion exchange filter and atleast one second ion exchange filter in the housing. The at least onefirst ion exchange filter and the at least one second ion exchangefilter are both negatively charged ion exchange filters and areconnected in series. The at least one first ion exchange filter isdifferent from the at least one second ion exchange filter.

In another aspect, the disclosure features a system that includes (1) adistillation column; and (2) an ion exchange filter unit downstream ofand in fluid communication with the distillation column. The ionexchange filter unit includes a housing and at least one first ionexchange filter and at least one second ion exchange filter in thehousing. The at least one first ion exchange filter and the at least onesecond ion exchange filter are both negatively charged ion exchangefilters and are connected in series. The at least first ion exchangefilter is different from the at least one second ion exchange filter.

Embodiments can include on or more of the following features.

In some embodiments, the organic solvent includes an alcohol (e.g.,isopropyl alcohol).

In some embodiments, the adsorbent includes a molecular sieve, a silicagel, activated alumina, activated carbon or an ion exchange resin.

In some embodiments, the filtration medium in the at least one firstfilter includes a polyolefin (e.g., high density polyethylene orpolytetrafluoroethylene), a polyamide, a fluoropolymer, or a copolymerthereof.

In some embodiments, the filtration medium in the at least one firstfilter has an average pore size from about 0.1 μm to 0.25 μm.

In some embodiments, the first filter unit includes two to five firstfilters. In some embodiments, the first filters are connected inparallel. In some embodiments, the at least one first filter is aparticle removal filter.

In some embodiments, the method further includes recirculating theorganic solvent before distilling the organic solvent in thedistillation column. In some embodiments, the recirculating includesmoving the organic solvent exiting the first filter unit to the at leastone column containing an adsorbent and subsequently passing the organicsolvent through the at least one column containing an adsorbent and thefirst filter unit.

In some embodiments, the method further includes passing the organicsolvent through a second filter unit downstream of the distillationcolumn, in which the second filter unit includes a second housing and atleast one second filter in the second housing, and the at least onesecond filter includes a filtration medium.

In some embodiments, the at least one first or second ion exchangefilter includes a filtration medium that includes a polyolefin, apolyamide, a fluoropolymer, or a copolymer thereof. In some embodiments,the filtration medium in the at least one first or second ion exchangefilter includes a polyethylene having sulfonate groups or apolytetrafluoroethylene having sulfonate groups, or a copolymer thereof.

In some embodiments, the ion exchange filter unit (e.g., third filterunit 124 shown in FIG. 1) includes two to five first ion exchangefilters. In some embodiments, the first ion exchange filters areconnected in parallel. In some embodiments, the at least one first ionexchange filter is capable of removing at least 90 wt % of Fe, Ni, Cr,Zn, and/or Cu from the organic solvent.

In some embodiments, the ion exchange filter unit (e.g., third filterunit 124 shown in FIG. 1) includes two to five second ion exchangefilters. In some embodiments, the second ion exchange filters areconnected in parallel. In some embodiments, the at least one second ionexchange filter is capable of removing at least 70 wt % of K, Na, and/orCa from the organic solvent.

In some embodiments, the method further includes passing the organicsolvent through a filter unit (e.g., second filter unit 122 shown inFIG. 1) in fluid communication with and between the distillation columnand the ion exchange filter unit (e.g., third filter unit 124 shown inFIG. 1). In some embodiments, the filter unit is between thedistillation column and the ion exchange filter unit includes a housingand at least one particle removal filter in the housing. In someembodiments, the at least one particle removal filter includes afiltration medium that includes a polyolefin, a polyamide, afluoropolymer (e.g., a polytetrafluoroethylene), or a copolymer thereof.In some embodiments, the at least one particle removal filter includes afiltration medium zo having an average pore size of from about 5 nm toabout 50 nm.

In some embodiments, the method further includes passing the organicsolvent through a filter unit (e.g., fourth filter unit 126 shown inFIG. 1) downstream of and in fluid communication with the ion exchangefilter unit (e.g., third filter unit 124 shown in FIG. 1). In someembodiments, the filter unit downstream of the ion exchange filter unitincludes a housing and at least one particle removal filter in thehousing. In some embodiments, the at least one particle removal filterin the filter unit downstream of the ion exchange filter unit includes afiltration medium that includes a polyolefin, a polyamide, afluoropolymer (e.g., a polytetrafluoroethylene), or a copolymer thereof.In some embodiments, the at least one particle removal filter in thefilter unit downstream of the ion exchange filter unit includes afiltration medium having an average pore size of from about 2 nm toabout 10 nm.

In some embodiments, the method further includes recirculating theorganic solvent exiting the filter unit downstream of the ion exchangefilter unit. In some embodiments, the recirculating includes moving theorganic solvent exiting the filter unit downstream of the ion exchangefilter unit to a storage tank and subsequently passing the organicsolvent from the storage tank through the ion exchange filter unit.

In some embodiments, the method further includes moving the purifiedsolvent to a packaging station.

In some embodiments, the purified organic solvent has a purity of atleast about 99.99%. In some embodiments, the purified organic solventhas a moisture content of is at most about 100 ppm. In some embodiments,the purified organic solvent includes metal impurities in a total amountof at most about 200 ppt of the purified organic solvent.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic diagram showing an example of a purificationsystem adopted in a method of purifying an organic solvent in accordancewith some embodiments of the present disclosure.

DETAILED DESCRIPTION OF THE DISCLOSURE

As defined herein, unless otherwise noted, all percentages expressedshould be understood to be percentages by weight to the total weight ofa composition. Unless otherwise noted, ambient temperature is defined tobe between about 16 and about 27 degrees Celsius (° C.). The term“solvent” mentioned herein, unless otherwise noted, refers to a singlesolvent or a combination of two or more (e.g., three or four) solvents.In the present disclosure, “ppm” means “parts-per-million”, “ppb” means“parts-per-billion” and “ppt” means “parts-per-trillion”, based on thetotal weight of a composition.

In general, the disclosure features systems and methods for purifying asolvent (e.g., an organic solvent). The solvent mentioned herein can beused in a wafer processing solution (such as a pre-wetting liquid, adeveloper solution, a rinsing solution, a cleaning solution, or astripping solution), or a solvent for a semiconductor material used inany semiconductor manufacturing process.

Prior to being subjected to a purification method of the presentdisclosure, a solvent may contain an undesirable amount of contaminantsand impurities (such as organic impurities, metal impurities, andmoisture). After the solvent is processed by the purification method ofthe present disclosure, substantial amounts of the contaminants andimpurities can be removed from the solvent. A pre-processed solvent isalso referred to herein as an “unpurified solvent”. The pre-processedsolvent can be synthesized in house or commercially available viapurchasing from a supplier. A post-processed solvent is also referred toherein as a “purified solvent”. A “purified solvent” can includeimpurities limited within predetermined ranges.

In general, the solvent mentioned herein can include at least one (e.g.,two, three, or four) organic solvent, such as an alcohol, an ether, ahydrocarbon, a halogenated hydrocarbon, an ester, a ketone, or acarbonate. Examples of suitable organic solvents include methanol,ethanol, 1-propanol, isopropanol, n-propanol, 2-methyl-1-propanol,n-butanol, 2-butanol, tert-butanol, 1-pentanol, 2-pentanol, 3-pentanol,n-hexanol, cyclohexanol, 2-methyl-2-butanol, 3-methyl-2-butanol,2-methyl-1-butanol, 3-methyl-1-butanol, 2-methyl-1-pentanol,2-methyl-2-pentanol, 2-methyl-3-pentanol, 3-methyl-1-pentanol,3-methyl-2-pentanol, 3-methyl-3-pentanol, 4-methyl-1-pentanol,4-methyl-2-pentanol, 2-ethyl-1-butanol, 2,2-dimethyl-3-pentanol,2,3-dimethyl-3-pentanol, 2,4-dimethyl-3-pentanol,4,4-dimethyl-2-pentanol, 3-ethyl-3-heptanol, 1-heptanol, 2-heptanol,3-heptanol, 2-methyl-2-hexanol, 2-methyl-3-hexanol, 5-methyl-1-hexanol,5-methyl-2-hexanol, 2-ethyl-1-hexanol, methylcyclohexanol,trimethylcyclohexanol, 4-methyl-3-heptanol, 6-methyl-2-heptanol,1-octanol, 2-octanol, 3-octanol, 2-propyl-1-pentanol,2,6-dimethyl-4-heptanol, 2-nonanol, 3,7-dimethyl-3-octanol, ethyleneglycol, propylene glycol, diethyl ether, dipropyl ether, diisopropylether, butyl methyl ether, butyl ethyl ether, butyl propyl ether,dibutyl ether, diisobutyl ether, tert-butyl methyl ether, tert-butylethyl ether, tert-butyl propyl ether, di-tert-butyl ether, dipentylether, diisoamyl ether, cyclopentyl methyl ether, cyclohexyl methylether, bromomethyl methyl ether, α,α-dichloromethyl methyl ether,chloromethyl ethyl ether, 2-chloroethyl methyl ether, 2-bromoethylmethyl ether, 2,2-dichloroethyl methyl ether, 2-chloroethyl ethyl ether,2-bromoethyl ethyl ether, (±)-1,2-dichloroethyl ethyl ether,2,2,2-trifluoroethyl ether, ethyl vinyl ether, butyl vinyl ether, allylethyl ether, allyl propyl ether, allyl butyl ether, diallyl ether,2-methoxypropene, ethyl-1-propenyl ether, cis-1-bromo-2-ethoxyethylene,2-chloroethyl vinyl ether, allyl-1,1,2,2-tetrafluoroethyl ether, octane,isooctane, nonane, decane, methylcyclohexane, decalin, xylene,ethylbenzene, diethylbenzene, cumene, sec-butylbenzene, cymene,dipentene, methyl pyruvate, monomethyl ether, propylene glycolmonomethyl ether, propylene glycol monoethyl ether, propylene glycolmonopropyl ether, propylene glycol monomethyl ether acetate, ethyllactate, methyl methoxypropionate, cyclopentanone, cyclohexanone,n-butyl acetate, y-butyrolactone, diisoamyl ether, isoamyl acetate,chloroform, dichloromethane, 1,4-dioxane, hexyl alcohol, 2-heptanone,isoamyl acetate, propylene carbonate, and tetrahydrofuran.

In some embodiments, the solvent is a pre-wetting liquid. Examples of apre-wetting liquid include at least one of cyclopentanone (CyPe),cyclohexanone (CyH), monomethyl ether, propylene glycol monomethyl ether(PGME), propylene glycol monoethyl ether (PGEE), propylene glycolmonomethyl ether acetate (PGMEA), propylene glycol monopropyl ether(PGPE), and ethyl lactate (EL). In some embodiments, the solvent can bea developer solution such as n-butyl acetate, or a rinsing liquid suchas 4-methyl-2-pentanol (MIBC). In some embodiments, the solvent can be arinse solvent used in a wafer manufacturing process, such as isopropylalcohol.

In some embodiments, the pre-processed or unpurified organic solvent canhave a purity of at most about 99% (e.g., at most about 98%, at mostabout 97%, at most about 96%, or at most about 95%). In someembodiments, the post-processed or purified organic solvent obtainedfrom the methods described herein can have a purity of at least about99.5% (e.g., at least about 99.9%, at least about 99.95%, at least about99.99%, at least about 99.995%, at least about 99.999%, at least about99.9995%, at least about 99.9999%, or 100%). As mentioned herein,“purity” refers to the weight percentage of the solvent in the totalweight of the liquid. The content of the organic solvent in a liquid canbe measured by using a gas chromatography mass spectrometry (GC-MS)device (e.g., a thermal desorption (TD) GC-MS device).

In some embodiments, the boiling point of the solvent described hereinis at most about 200° C. (e.g., at most about 150° C.) or at least about50° C. (e.g., at least about 100° C.) from a point of improvingmanufacturing yield of a semiconductor chip. For is example, when thesolvent is isopropanol, its boiling point is about 82.5° C. In thisdisclosure, the boiling point means a boiling point measured at 1 atm.

In general, impurities contained in a pre-processed organic solvent caninclude metallic impurities, particles, and others such as organicimpurities and moisture.

As described herein, metal impurities can be in a form of a solid (e.g.,metal simplex, particulate metal-containing compound, and the like). Insome embodiments, metal impurities can include a metal selected from thegroup consisting of alkali metals, alkaline earth metals, main groupmetals, transition metals, and lanthanide metals. Examples of commonmetallic impurities include heavy metals such as copper (Cu), iron (Fe),aluminum (Al), chromium (Cr), lead (Pb), nickel (Ni), zinc (Zn), andlead (Pb); and alkali or alkaline earth metals such as sodium (Na),potassium (K), and calcium (Ca). Depending on the type of metal, metalimpurities can deteriorate oxide integrity, degrade MOS gate stacks, andreduce lifetime of devices. In some embodiments, the content of eachmetal component in the pre-processed solvent ranges from about 0.1 toabout 1000 ppt (e.g., from about 200 to about 1000 ppt or from about 500to about 1000 ppt).

In an organic solvent purified by the methods described herein, thetotal trace metal content is preferred to be within a predeterminedrange of from 0 (e.g., at least about 1 ppt, at least about 5 ppt, or atleast about 10 ppt) to at most about 200 ppt (e.g., at most about 180ppt, at most about 160 ppt, at most about 150 ppt, at most about 140ppt, at most about 120 ppt, at most about 100 ppt, at most about 50 ppt,or at most about 20 ppt) in mass, and the amount of each trace metal(e.g., Fe, Ni, Cr, Zn, Cu, K, Na, or Ca) is preferred to be within apredetermined range of from 0 (e.g., at least about 1 ppt, at leastabout 2 ppt, or at least about 3 ppt) to at most about 50 ppt (e.g., atmost about 40 ppt, at most about 30 ppt, at most about 20 ppt, at mostabout 15 ppt, at most about 10 ppt, at most about 8 ppt, at most about 6ppt, at most about 5 ppt, at most about 4 ppt, at most about 3 ppt, orat most about 2 ppt) in mass.

In the present disclosure, substances having a size of 0.03 pm orgreater are referred to as “particles” or “particulates”. Examples ofparticles include dust, dirt, organic solid matters, and inorganic solidmatters. The particles can also include impurities of colloidalizedmetal atoms. The type of the metal atoms that are easily zocolloidalized is not particularly limited, and can include at least onemetal atom selected from the group consisting of Na, K, Ca, Fe, Cu, Mg,Mn, Li, Al, Cr, Ni, Zn, and Pb. In an organic solvent purified by themethods described herein, the total number of the particles having asize of 0.03 pm or more (e.g., 0.05 μm or more) is preferred to bewithin a predetermined range of at most 100 (e.g., at most 80, at most60, at most 50, at most 40, at most 20, at most about 10, at most about5, at most about 1, or 0) per 1 ml of the solvent. The number of“particles” in a liquid medium can be counted by a light scattering typein-liquid particle counter and is referred as LPC (liquid particlecount).

As described herein, organic impurities are different from the organicsolvent and refer to organic matters that are contained in the contentof 5000 mass ppm or smaller with respect to the total mass of the liquidcontaining the organic solvent and the organic impurities. Organicimpurities can be volatile organic compounds that are present in ambientair even inside a clean-room. Some of the organic impurities originatefrom shipping and storage equipment, while some are presented in a rawmaterial from the start. Other examples of organic impurities include aby-product generated when the organic solvent is synthesized and/or anunreacted reactant. Examples of organic impurities include aliphatichydrocarbons (e.g., C₈-C₂₄ alkanes or alkenes having 8 or more carbons),aromatic hydrocarbons, ethers, esters, and aldehydes.

The total content of the organic impurities in a purified organicsolvent is not particularly limited. From a point of improving themanufacturing yield of a semiconductor device, the total content of theorganic impurities can be at most about 1000 ppb (e.g., at most about500 ppb, at most about 400 ppb, at most about 300 ppb, at most about 200ppb, at most about 100 ppb, at most about 50 ppb, at most about 20 ppb,at most about 10 ppb) and/or at least about 0.1 ppb (at least about 0.5ppb or at least about 1 ppb) of the purified organic solvent. In someembodiments, the organic solvent is free of any organic impurities. Thecontent of the organic impurities in the solvent described herein can bemeasured by using a gas chromatography mass spectrometry (GC-MS) device(e.g., a thermal desorption (TD) GC-MS device).

In some embodiments, the total amount of the moisture or water contentcan be at most about 100 ppm (e.g., at most about 50 ppm, at most about40 ppm, at most about 30 ppm, at most about 20 ppm, at most about 10ppm, at most about 5 ppm, at most about 2 ppm, at most about 1 ppm, atmost about 500 ppb, at most about 100 ppb, or at most about 10 ppb)and/or at least about 1 ppb (e.g., at least about 1 ppm or at leastabout 20 ppm) of the purified organic solvent. In some embodiments, thepurified organic solvent is free of water. The moisture or water contentin the solvent described herein can be measured by using a gaschromatography mass spectrometry (GC-MS) device.

FIG. 1 is a schematic diagram showing a configuration of a purificationsystem according to some embodiments of the present disclosure. As shownin FIG. 1, the purification system 10 includes supply unit 110,dehydration columns 112 a and 112 b, first filter unit 114, distillationcolumn 120, storage tank 130, second filter unit 122, third filter unit124, fourth filter unit 126, and packaging station 140, all of which arein fluid communication with each other (e.g., through one or more pipesor conduits). Purification system 10 also includes an optional firstrecirculation loop 150 connecting supply unit 110, dehydration columns112 a and 112 b, and first filter unit 114, and an optional secondrecirculation loop 160 connecting storage tank 130, second filter unit122, third filter unit 124, and fourth filter unit 126. In general,purification system 10 can include other components (such as pumps,temperature control units, supply ports, outflow ports, or valves) thatare not shown in FIG. 1.

In general, supply unit 110 is configured to hold or transport astarting material is (e.g., a pre-processed or unpurified organicsolvent). The starting material can be processed by purification system10 to produce or manufacture a purified organic solvent in which thenumber of unwanted contaminants (e.g., particulates, organic impurities,metallic impurities, and moisture) are limited within predeterminedranges. The type of supply unit 110 is not particularly limited as longas it continuously or intermittently supplies the starting material tothe other components of purification system 10. In some embodiments,supply unit 110 can be a tank, such as a stationary tank or a mobiletank. In some embodiments, supply unit 110 can include a materialreceiving tank, a sensor such as a level gauge (not shown), a pump (notshown), and/or a valve (not shown) for controlling the flow of thestarting material (not shown). In FIG. 1, purification system 10includes one supply unit 110. However, in some embodiments, a pluralityof supply units 110 can be provided (e.g., in parallel or series) foreach type of starting materials to be processed by purification system10.

Purification system 10 can include at least one pre-distillationfiltration system 20 and at least one post-distillation filtrationsystem 30. In general, pre-distillation filtration system 20 performs aninitial filtration of the starting material (e.g., unpurified organicsolvent) to remove moisture and/or large particles before distillation,and post-distillation filtration system 30 performs a filtration afterdistillation to remove any remaining impurities (e.g., metal or organicimpurities) and fine particles to obtain a ultra-high purity organicsolvent. In some embodiments, each of pre-distillation filtration system20 and post-distillation filtration system 30 can include one or morefilter units (each of which can include a filter housing and one or morefilters (e.g., 1-20 filters)) in the filter housing, and certain othervessels (e.g., a storage tank) and impurity-removal columns (such as adehydration column). For example, pre-distillation filtration system 20shown in FIG. 1 includes supply unit 110, dehydration columns 112 a/112b, and first filter unit 114, and post-distillation filtration system 30shown in FIG. 1 includes storage tank 130, second filter unit 122, thirdfilter unit 124, and fourth filter unit 126. Distillation column 120shown in FIG. 1 is generally used to remove the majority of the organicand metal impurities and particles.

In some embodiments, purification system 10 can optionally include oneor more temperature control units (not shown in FIG. 1) for setting ormaintaining the temperature of the organic solvent within a certaintemperature range such that the organic solvent is maintained at asubstantially consistent temperature during certain part of thepurification process. As described herein, a temperature control unitcan include, but are not limited to, a commercial re-circulatingheating/cooling unit, a condenser, or a heat exchanger, which can beinstalled, for example, on distillation column 120 or on a conduit atany suitable location in purification system 10.

In some embodiments, an organic solvent can be purified by purificationsystem 10 at ambient temperature. In such embodiments, purificationsystem 10 may not need a temperature control unit except for those thatmay be needed for distillation column 120.

In some embodiments, purification system 10 can include at least one(e.g., two or three) column containing an adsorbent (e.g., dehydrationcolumns) to remove moisture or certain other impurities in theunpurified organic solvent. In some embodiments, the adsorbent in such acolumn can include a molecular sieve (e.g., zeolite 3A, zeolite 4A, orzeolite 5A), a silica gel, activated alumina, activated carbon or an ionexchange resin. In some embodiments, when one column containing anadsorbent is not sufficient to lower moisture in the organic solvent toa desired level (e.g., at most about 100 ppm), two or more of suchcolumns can be used. For example, FIG. 1 shows that two dehydrationcolumns 112 a and 112 b are used in purification system 10. In suchembodiments, dehydration columns 112 a and 112 b can be in fluidcommunication with each other and are connected in series.

In some embodiments, each filter unit in purification system 10 caninclude a filter housing and one or more (e.g., 2, 3, 4, or 5) filtersin the filter housing. Each filter can include a filtration medium madefrom a suitable material and having an appropriate average pore size.The filters can be arranged in parallel or in series in the filterhousing. During use, when two filters are arranged in parallel, asolvent to be purified passes these two filters in parallel (i.e.,substantially at the same time). On the other hand, when two filters arearranged in series, a solvent to be purified passes these two filterssequentially during use. In some embodiments, some filter units caninclude a plurality of filters in parallel in the filter housing toincrease flow rate and improve productivity.

For example, purification system 10 shown in FIG. 1 includes four filterunits (i.e., units 114, 122, 124, and 126), each of which includes afilter housing and one or more filters in the filter housing. In otherembodiments, purification system 10 can also include other purificationmodules in addition to the four filter units shown in FIG. 1.

Referring to FIG. 1, filter units 114, 122, 124, and 126 can bedifferent in functionality or property and offer different purificationtreatments. In some embodiments, each filter unit can independently beselected from the group consisting of a particle removal filter, an ionexchange filter, and an ion absorption filter. In some embodiments, thefilters accommodated within each of filter units 114, 122, 124, and 126can have the same or similar purification function, physiochemicalproperties, pore size and/or construction material.

In some embodiments, purification system 10 can include at least one(e.g., two or three) first filter unit 114 between dehydration column112 b and distillation column 120 and in fluid communication withcolumns 112 b and 120. First filter unit 114 can include a filterhousing and at least one (e.g., 2, 3, 4, or 5) filter in the filterhousing. In some embodiments, when first filter unit 114 includes two ormore filters, these filters can be arranged in parallel to improve flowrate and productivity.

In some embodiments, the filters in first filter unit 114 can be aparticle removal filter to remove relatively large particles from theorganic solvent. In some embodiments, the filters in first filter unit114 can include a filtration medium having an average pore size of atmost about 0.25 μm or 250 nm (e.g., at most about 240 nm, at most about220 nm, at most about 200 nm, at most about 180 nm, at most about 160nm, or at most about 150 nm) and/or at least about 0.1 μm or 100 nm(e.g., at least about 110 nm, at least about 120 nm, at least about 130nm, at least about 140 nm, or at least about 150 nm). Within the aboverange, it is possible to reliably remove foreign matters such asimpurities or aggregates contained in the organic solvent whilesuppressing clogging of the filters in first filter unit 114.

Examples of suitable materials of the filtration media in the filters infirst filter unit 114 include a fluoropolymer (e.g.,polytetrafluoroethylene (PTFE), perfluoroalkoxy alkane polymers (PFA),or a modified polytetrafluoroethylene (MPTFE)), a polyamide such asnylon (e.g., nylon 6 or nylon 66), a polyolefin (including high densityand ultrahigh molecular weight resins) such as polyethylene (PE) andpolypropylene (PP), or a copolymer thereof. For example, the filtrationmedium in a particle removal filter can be made of at least one polymerselected from the group consisting of polypropylene (e.g., high densitypolypropylene), polyethylene (e.g., high density polyethylene (HDPE), orultra high molecular weight polyethylene (UPE)), nylon,polytetrafluoroethylene, or a perfluoroalkoxy alkane polymer. A filtermade of the above materials can effectively remove foreign matters(e.g., those having high polarity) which are likely to cause residuedefects and/or particle defects, and to efficiently reduce the contentof the metal components in the organic solvent.

In some embodiments, at least some (e.g., all) of the filters can bearranged in first filter unit 114 in parallel and the remaining filtersin first filter unit 114 (if any) can be arranged in series. In someembodiments, first filter unit 114 can include two or three filters thatare arranged in parallel, have an average pore size of about 100 nm, andinclude a filtration medium made from polytetrafluoroethylene.

Without wishing to be bound by theory, it is believed that using acombination of dehydration column and first filter unit in purificationsystem 10 can significantly lower the moisture content of the purifiedorganic solvent without increasing the amounts of particles and otherimpurities in the purified organic solvent. For example, when using acombination of dehydration column and first filter unit in purificationsystem 10, the purified organic solvent can have a moisture content ofat most about 100 ppm (to at least about 1 ppm. Further, without wishingto be bound by theory, it is believed that a dehydration column mayrelease contaminants (e.g., particles) during use and using first filterunit 114 can significantly lower the amount of such contaminants in thepurified zo organic solvent.

During the purification process, if the purity level of the organicsolvent exiting first filter unit 114 meets the predeterminedrequirements (e.g., having a moisture content of at most about 100 ppm),the organic solvent can be transferred to distillation column 120 fordistillation. On the other hand, if the purity level of the organicsolvent exiting first filter unit 114 does not meet the predeterminedrequirements, the organic solvent can be transferred back to supply unit110 through optional first recirculation loop 150 and be purified againby dehydration columns 112 a/112 b and first filter unit 114.

In some embodiments, purification system 10 includes at least one (e.g.,two or three) distillation column 120 between pre-filtration system 20and post-distillation system 30. As shown in FIG. 1, distillation column120 is disposed between first filter unit 114 and storage 130 and is influid communication with unit 114 and tank 130. In general, distillationcolumn 120 can be any suitable distillation column known in the art andis used to purify the organic solvent through distillation to remove themajority of the organic and metal impurities and particles.

In some embodiments, purification system 10 includes at least one (e.g.,two or three) storage tank 130 between distillation column 120 andsecond filter unit 122 and is in fluid communication with column 120 andunit 122. In general, storage tank 130 can be any suitable storage tankknown in the art and can be used to store the organic solvent. In someembodiments, storage tank 130 can be filled with nitrogen to minimizethe moisture and oxidation of the solvent stored in the tank. During thepurification is process, the organic solvent exiting distillation column120 can be first transferred to storage tank 130, and then can passthrough filter units 122, 124, and 126 to remove impurities. If thepurity level of the organic solvent exiting filter unit 126 meets thepredetermined requirements (e.g., having a purity of at least about99.99%, a moisture content of at most about 100 ppm, and/or metalimpurities in a total amount of at most zo about 200 ppt), the organicsolvent can be transferred to package station 140. On the other hand, ifthe purity level of the purified organic solvent does not meet thepredetermined requirements, the organic solvent can then be transferredback to storage tank 130 through optional second recirculation loop 160and be purified again by filter units 122, 124, and 126.

In general, storage tank 130 can be any suitable vessel for storing achemical liquid. In some embodiments, storage tank 130 can have asuitable volume. For example, storage tank 130 can have a volume of atleast about 1000 liters (e.g., at least about 2000 liters, at leastabout 3000 liters, or at least about 5000 liters) and/or at most about30,000 liters (e.g., at most about 25,000 liters, at most about 20,000liters, at most about 15,000 liters, or at most about 10,000 liters).

In some embodiments, purification system 10 can include at least one(e.g., two or three) second filter unit 122 between storage tank 130 andthird filter unit 124 and in fluid communication with tank 130 and unit124. In some embodiments, second filter unit 122 can include a filterhousing and at least one (e.g., 2, 3, 4, or 5) filters in the filterhousing. The filters in second filter unit 122 can be a particle removalfilter to remove relative small particles from the organic solvent. Insome embodiments, the filters in second filter unit 122 can include afiltration medium having an average pore size of at most about 50 nm(e.g., at most about 45 nm, at most about 40 nm, at most about 35 nm, atmost about 30 nm, at most about 25 nm, or at most about 20 nm) and/or atleast about 5 nm (e.g., at least about 10 nm, at least about 15 nm, atleast about 20 nm, at least about 25 nm, or at least about 30 nm). Insome embodiments, the average pore size of the filtration medium in thefilters in second filter unit 122 can be smaller than the average poresize of the filtration medium in the filters in first filter unit 114.In such embodiments, second filter unit 122 can be used to removeparticles smaller than those removed by first filter unit 114.

Examples of suitable materials of the filtration media in the filters insecond filter unit 122 include a fluoropolymer (e.g.,polytetrafluoroethylene (PTFE), perfluoroalkoxy zo alkane polymers(PFA), or a modified polytetrafluoroethylene (MPTFE)), a polyamide suchas nylon (e.g., nylon 6 or nylon 66), a polyolefin (including highdensity and ultrahigh molecular weight resins) such as polyethylene (PE)and polypropylene (PP), or a copolymer thereof. For example, thefiltration medium in a particle removal filter can be made of at leastone polymer selected from the group consisting of polypropylene (e.g.,high density polypropylene), polyethylene (e.g., high densitypolyethylene (HDPE), or ultra high molecular weight polyethylene (UPE)),nylon, polytetrafluoroethylene, or a perfluoroalkoxy alkane polymer.

In some embodiments, at least some (e.g., all) of the filters can bearranged in second filter unit 122 in parallel and the remaining filtersin second filter unit 122 (if any) can be arranged in series. In someembodiments, second filter unit 122 can include two or three filtersthat are arranged in parallel, have an average pore size of about 50 nm,and include a filtration medium made from polytetrafluoroethylene.

In some embodiments, purification system 10 can include at least one(e.g., two or three) third filter unit 124. In some embodiments, thirdfilter unit 124 can be an ion exchange filter unit that includes atleast one (e.g., 2, 3, 4, or 5) first ion exchange filter and at leastone (e.g., 2, 3, 4, or 5) second ion exchange filter in the housing. Insome embodiments, the at least one first ion exchange filter and the atleast one second ion exchange filter are both negatively charged ionexchange filters or cationic ion exchange filters (i.e., including oneor more filtration medium containing a negatively charged ion exchangeresin) and are connected in series. When there are more than one firstion exchange filter, the multiple first ion exchange filters can beconnected in parallel to increase flow rate and productivity. When thereare more than one second ion exchange filter, the multiple second ionexchange filters can be connected in parallel to increase flow rate andproductivity.

In general, the at least one first ion exchange filter is different fromthe at least one second ion exchange filter (e.g., containing differentfiltration media). In some embodiments, the at least one first ionexchange filter can be capable of primarily removing heavy metals (e.g.,Fe, Ni, Cr, Zn, or Cu), while the at least one second ion exchangefilter can be capable of primarily removing alkali or alkaline earthmetals (e.g., K, Na, or Ca). In some embodiments, the first ion exchangefilter can be capable of removing at least about 90 wt % (e.g., at leastabout 92 wt % or at least about 95 wt %) of one or more heavy metalsand/or at most about 10 wt % (e.g., at most about 8 wt % or at mostabout 5 wt %) of one or more alkali or alkaline earth metals in theorganic solvent. In some embodiments, the second ion exchange filter canbe capable of removing at least about 70 wt % (e.g., at least about 75wt %, at least about 80 wt %, at least about 85 wt %, or at least about90 wt %) one or more alkali or alkaline earth metals and/or at mostabout 30 wt% (e.g., at most about 25 wt %, at most about 20 wt %, atmost about 15 wt %, or at most about 10 wt %) one or more heavy metalsin the organic solvent.

In some embodiments, it is preferable that the at least one second ionexchange filter is disposed downstream of the at least one first ionexchange filter. Without wishing to be bound by theory, it is believedthat, in such embodiments, heavy metals in the organic solvent can beremoved first, which facilitates the removal of alkali or alkaline earthmetals because residual heavy metals in the organic solvent may impedethe removal of alkali or alkaline earth metals by the at least onesecond ion exchange filter. In some embodiments, the sequence of the atleast one first and second ion exchange filters in third filter unit 124can be reversed.

In some embodiments, the at least one first or second ion exchangefilters in filter unit 124 can include one or more negatively chargedion exchange resin membranes as a filtration medium to remove positivelycharged particles and/or cationic metal ions from the organic solvent.The negatively charged ion-exchange resin membrane used in the presentdisclosure is not particularly limited, and filters including an ionexchange resin having a suitable ion-exchange group immobilized to aresin membrane can be used. Examples of such ion-exchange resinmembranes include strongly acidic cation-exchange resins having acation-exchange group (such as a sulfonic acid or sulfonate group)chemically modified on the resin membrane. Examples of suitable resinmembranes include those containing cellulose, diatomaceous earth, apolyamide (e.g., nylon), a polyolefin (such as polyethylene (e.g., highdensity polyethylene or ultra high molecular weight polyethylene),polypropylene, or polystyrene), a resin having an imide group, a resinhaving an amide group and an imide group, a fluoropolymer (e.g., apolytetrafluoroethylene or a perfluoroalkoxy alkane polymer), or acopolymer or combination thereof. In some embodiments, the ion-exchangeresin membrane can be a membrane having an integral structure of aparticle-removing membrane and an ion-exchange resin membrane.Polyalkylene (e.g., PE, PP, or PTFE) membranes with a cation-exchangegroup (e.g., a sulfonate group) chemically modified thereon arepreferred. Filters with cation-exchange resin membranes used in thepresent disclosure can be commercially available filters with metal ionremoval functionality. Commercial example of such a cation-exchangefilter include IonKleen filters available from Pall Corporation (PortWashington, N.Y.) and Protego Plus filters available from Entegris(Billerica, Mass.). These filters can be selected based on the ionexchange efficiency and have an estimated pore size in the range ofabout 100 nm to about 500 nm.

Examples of the shape of the membrane material in the at least one firstor second ion exchange filters in filter unit 124 include a pleatedtype, a flat membrane type, a hollow fiber type, a porous body asdescribed in JP-A No. 2003-112060 and the like. In some embodiments,when the ion exchange membrane has porosity, it is also possible toremove at least a portion of the fine particles in the organic solvent.

In some embodiments, the at least one first ion exchange filter infilter unit 124 can include a filtration medium that includes apolyethylene having sulfonate groups, a polytetrafluoroethylene havingsulfonate groups, or a copolymer thereof, which is capable of primarilyremoving heavy metals (e.g., Fe, Ni, Cr, Zn, or Cu). A commercialexample of such a filter is an IonKleen filter (such as IonKleen SLfilters) from Pall is Corporation (Port Washington, N.Y.). In someembodiments, filter unit 124 can include two or three such first ionexchange filters connected in parallel to increase productivity.

In some embodiments, the at least one second ion exchange filter infilter unit 124 can include a filtration medium that includes apolyethylene having sulfonate groups, a polytetrafluoroethylene havingsulfonate groups, or a copolymer thereof, which is capable of primarilyremoving alkali or alkaline earth metals (e.g., K, Na, or Ca).Commercial examples of such a filter include Protego Plus filters (suchas Protego Plus IPA filters) and Protego AT 5 nm/Ionex combo filtersavailable from Entegris (Billerica, Mass.). In some embodiments, thirdfilter unit 124 can include two or three such second ion exchangefilters connected in parallel to increase productivity.

Without wishing to be bound by theory, the inventors surprisingly foundthat including two different types of ion exchange filters in thirdfilter unit 124 can significantly reduce the amount of metal impurities(e.g., to a total amount of at most about 200 ppt) in the purifiedorganic solvent, compared to a system in which only one type of ionexchange filter is used.

In some embodiments, purification system 10 can include at least one(e.g., two or three) fourth filter unit 126 between third filter unit124 and packaging station 140 (i.e., downstream of unit 124), and influid communication with unit 124 and station 140. In some embodiments,fourth filter unit 126 can include a filter housing and at least one(e.g., 2, 3, 4, or 5) filters in the filter housing. The filters infourth filter unit 126 can be a particle removal filter to removerelative small particles from the organic solvent. In some embodiments,the filters in fourth filter unit 126 can include a filtration mediumhaving an average pore size of at most about 10 nm (e.g., at most about9 nm, at most about 8 nm, at most about 7 nm, at most about 6 nm, atmost about 5 nm, or at most about 4 nm) and/or at least about 2 nm(e.g., at least about 3 nm, at least about 4 nm, or at least about 5nm). In some embodiments, the average pore size of the filtration mediumin the filters in fourth filter unit 126 can be smaller than the averagepore size of the filtration medium in the filters in second filter unit122. In such embodiments, fourth is filter unit 126 can be used toremove particles smaller than those removed by second filter unit 122.

Examples of suitable materials of the filtration media in the filters infourth filter unit 126 include a fluoropolymer (e.g.,polytetrafluoroethylene (PTFE), perfluoroalkoxy zo alkane polymers(PFA), or a modified polytetrafluoroethylene (MPTFE)), a polyamide suchas nylon (e.g., nylon 6 or nylon 66), a polyolefin (including highdensity and ultrahigh molecular weight resins) such as polyethylene (PE)and polypropylene (PP), or a copolymer thereof. For example, thefiltration medium in a particle removal filter can be made of at leastone polymer selected from the group consisting of polypropylene (e.g.,high density polypropylene), polyethylene (e.g., high densitypolyethylene (HDPE), or ultra high molecular weight polyethylene (UPE)),nylon, polytetrafluoroethylene, or a perfluoroalkoxy alkane polymer. Afilter made of the above material can effectively remove foreign matters(e.g., those having high polarity) which are likely to cause residuedefects and/or particle defects, and to efficiently reduce the contentof the metal components in the organic solvent.

In some embodiments, at least some (e.g., all) of the filters can bearranged in fourth filter unit 126 in parallel and the remaining filtersin fourth filter unit 126 (if any) can be arranged in series. In someembodiments, fourth filter unit 126 can include two or three filtersthat are arranged in parallel, have an average pore size of about 10 nm,and include a filtration medium made from polytetrafluoroethylene.

In some embodiments, purification system 10 can optionally include arecirculation conduit to form first recirculation loop 150 forrecirculating a partially-purified organic solvent back to supply unit110, which can be purified by dehydration columns 112 a/112 b and firstfilter unit 114 again. In some embodiments, purification system 10 canoptionally include a recirculation conduit to form second recirculationloop 160 for recirculating a partially-purified organic solvent back tostorage tank 130, which can be purified by filter units 122, 124, and126 again. In some embodiments, the partially-purified organic solventis recirculated through first recirculation loop 150 or secondrecirculation loop 160 at least two times (e.g., at least three times,at least four times, or at least five times) before the organic solventis transferred to packaging station 140.

In some embodiments, filter units 114, 122, 124, and 126 in purificationsystem 110 may not include filter housings, and the filters in filterunits 114, 122, 124, and 126 can be configured un-compartmentalized inpurification system 10. For example, purification system 10 can be amultistage system including replaceable filters (e.g., those in filterunits 114, 122, 124, and 126) that are concatenated together insidepurification system 10, and the organic solvent can be caused to cascadethrough these filters.

In some embodiments, packaging station 140 can be a mobile storage tank(e.g., a tank on a tanker) or a fixed storage tank. In some embodiments,packaging station 140 can be a fluoropolymer lined equipment (e.g., theinner surface of which can include a fluoropolymer such as a PTFE). Insome embodiments, packaging station 140 can have a volume of at leastabout 100 liters (e.g., at least about 200 liters, at least about 300liters, or at least about 500 liters) and/or at most about 1,500 liters(e.g., at most about 1200 liters, at most about 1000 liters, at mostabout 900 liters, at most about 800 liters, at most about 700 liters, orat most about 600 liters).

The present disclosure also features methods of purifying a solvent(e.g., an organic solvent such as isopropyl alcohol). In someembodiments, the purification method can include (1) passing the organicsolvent through at least one column containing an adsorbent (e.g.,dehydration columns 112 a/112 b shown in FIG. 1) to remove residualmoisture in the organic solvent, (2) passing the organic solvent througha first filter unit (e.g., first filter unit 114 shown in FIG. 1), inwhich the first filter unit includes a first housing and at least onefilter in the first housing, and the at least one filter includes afiltration medium; and (3) distilling the organic solvent in adistillation column (e.g., distillation column 120 shown in FIG. 1) toobtain a purified organic solvent.

In some embodiments, the purification method can include (1) distillingthe organic solvent in a distillation column to obtain a distilledorganic solvent; and (2) passing the distilled organic solvent throughan ion exchange filter unit (e.g., third filter unit 124 shown inFIG. 1) to obtain a purified organic solvent, in which the ion exchangefilter unit includes a housing, and at least one first ion exchangefilter and at least one second ion exchange filter in the housing; theat least one first ion exchange filter and the at least one second ionexchange filter are both negatively charged ion exchange filters and areconnected in series; and the at least one first ion exchange filter isdifferent from the at least one second ion exchange filter.

For example, referring to FIG. 1, an unpurified or pre-processed solvent(i.e., a starting material) can be purified by purification system 10 bypassing the solvent from supply unit 110 through dehydration columns 112a/112 b and first filter units 114 to distillation column 120,distilling the solvent in distillation column 120, transferring thesolvent exiting distillation column 120 to storage tank 130, and passingthe solvent from storage tank 130 through filter units 122, 124, and 126to packaging station 140.

In some embodiments, the purification methods described herein caninclude recirculating the solvent through recirculation loop 150 inpre-distillation filtration system 20 (e.g., through supply unit 110,dehydration columns 112 a/112 b, and first filter unit 114) at least onetime (e.g., two or three times) before transferring thepartially-purified solvent to distillation column 120. For example, therecirculating can include moving the organic solvent exiting firstfilter unit 114 to supply unit 110 and subsequently passing the organicsolvent through dehydration columns 112 a/112 b (which include anadsorbent) and first filter unit 114 one or more times until themoisture level in the organic solvent is within a predetermined range.

In some embodiments, the purification methods described herein caninclude recirculating the solvent through recirculation loop 160 inpost-distillation filtration system 30 (e.g., through filter units 122,124, and 126, and storage tank 130) at least one time (e.g., two orthree times) before transferring the purified solvent to packagingstation 140. For example, the recirculating can include moving theorganic solvent exiting fourth filter unit 126 to storage tank 130 andsubsequently passing the organic solvent through second filter unit 122,third filter unit 124 (which can be an ion exchange filter unit thatincludes two different types of ion exchange filters), and fourth filterunit 126 one or more times until the purity and the total amount oftrace metals in the organic solvent are within predetermined ranges.

When the number of particles and the amount of impurities detected fromthe purified solvent at the end of the purification process arecontrolled within predetermined ranges, an ultra-high purity solvent(e.g., having a purity of at least about 99.99%, a moisture content ofat most about 100 ppm, and/or metal impurities in a total amount of atmost about 200 ppt) is produced. Subsequently, the ultra-high puritysolvent can be transferred to either packaging station 140 for storageor to a manufacturing process for making a semiconductor article.

In some embodiments, the solvent purified by the methods and systemsdescribed herein can form a film or coating having an on-wafer particlecount of at most about 500 (e.g., at most about 450, at most about 400,at most about 350, at most about 300, at most about 250, at most about200, at most about 150, at most about 100, at most about 50 or at mostabout 25) or 0 on an entire wafer (e.g., a 12-inch wafer). In someembodiments, the solvent purified by the methods and systems describedherein can form a film or coating having an on-wafer metal count (e.g.,either a total on-wafer metal count or an on-wafer metal count of aspecific metal such as Fe or Ni) of at most about 100 (e.g., at mostabout 90, at most about 80, at most about 70, at most about 60, at mostabout 50, at most about 40, at most about 30, at most about 20, or atmost about 10) or 0 on an entire wafer (e.g., a 12-inch wafer). In someembodiments, the solvent purified by the methods and systems describedherein can form a film or coating having an defect density (i.e., basedon the total count of on-wafer metal and particles) of at most about 1.5(e.g., at most about 1.4, at most about 1.2, at most about 1, at mostabout 0.8, at most about 0.6, at most about 0.5, at most about 0.4, atmost about 0.2, at most about 0.1, at most about 0.07, at most about0.05, at most about 0.03, at most about 0.02, at most about 0.01, atmost about 0.007, at most about 0.005, at most about 0.004, at mostabout 0.003) or 0 per square centimeter on an entire wafer (e.g., a12-inch wafer).

In some embodiments, the solvent can be purified by the methods andsystems described herein at a relatively high flow rate. For example,the solvent can be purified at a flow rate of at least about 1 L/min(e.g., at least about 2 L/min, at least about 4 L/min, at least about 5L/min, at least about 6 L/min, at least about 8 L/min, at least about 10L/min, or at least about 15 L/min) and/or at most about 50 L/min (e.g.,at most about 45 L/min, at most about 40 L/min, at most about 35 L/min,at most about 30 L/min, at most about 25 L/min, at most about 20 L/min,or at most about 15 L/min) through purification system 10. In general,the flow rate for purifying a solvent can vary depending on a number offactors, including the nature and viscosity of the solvent to bepurified, the temperature, the number of the filters (e.g., thosearranged in parallel), the type and number of other equipment used inthe purification process. Without wishing to be bound by theory, it isbelieved that the flow rate of the solvent to be purified cannot be toohigh to minimize defects on a wafer and to minimize buildup of staticelectric charges in the inner surface of a conduit or vessel, which canerode the conduit or vessel.

The present disclosure is illustrated in more detail with reference tothe following examples, which are for illustrative purposes and shouldnot be construed as limiting the scope of the present disclosure.

EXAMPLES General Description of Trace Metal Measurement

The total trace metal concentration in a solvent sample was tested usingICP-MS (inductively coupled plasma mass spectrometry (ICP-MS). Using aFujifilm developed method, each sample was tested for the presence of 36metal species, the detection limit was metal specific, but the typicaldetection limits were in the range of 0.00010-0.030 ppb.

General Description of Trace Moisture and Organic Impurities Measurement

The trace moisture and organic impurities in a liquid sample aremeasured by Thermal Desorption-Gas Chromatography/Mass Spectrometry(TD-GC/MS). A small volume of a liquid sample is injected into a thermaldesorption tube containing a sorbent, and put into a thermal desorber.The sample is heated, then injected into the GC/MS unit where the samplemixture is separated into its components and components are identifiedby mass.

Example 1

Isopropyl alcohol (IPA) was purified in the purification system shown inFIG. 1. The test results are summarized in Table 1 below.

TABLE 1 Before After Contaminants Purification Purification Purity (%)99.99 >99.99 Water (ppm) 400 40 n-Propanol (ppm) 405.2 7 Acetone (ppm)170.8 8.8 Total Organics + C6 (ppb) 1127.81 349.88 Al (ppb) 1 0.005 As(ppb) 8.9 0.008 Sb (ppb) 1 0.004 Ba (ppb) 1 0.002 Be (ppb) 1 0.008 Bi(ppb) 1 0.004 B (ppb) 1 0.037 Cd (ppb) 1 0.004 Ca (ppb) 1 0.02 Cr (ppb)1.6 0.005 Co (ppb) 1 0.004 Cu (ppb) 1 0.004 Ga (ppb) 1 0.004 Ge (ppb) 10.004 Au (ppb) 1 0.002 In (ppb) 1 0.004 Fe (ppb) 5.8 0.009 Pb (ppb) 10.003 Li (ppb) 1 0.005 Mg (ppb) 1 0.004 Mn (ppb) 1 0.004 Mo (ppb) 10.003 Ni (ppb) 1 0.005 Nb (ppb) 1 0.004 K (ppb) 1.9 0.004 Ru (ppb) 10.004 Ag (ppb) 1 0.004 Na (ppb) 3.6 0.005 Sr (ppb) 1 0.003 Ta (ppb) 10.002 Tl (ppb) 1 0.004 Sn (ppb) 1 0.003 Ti (ppb) 1 0.004 V (ppb) 1 0.004Zn (ppb) 14.3 0.009 Zr (ppb) 1 0.003“Total Organics+C6” refers to the total amount of organic impuritieshaving six carbons or more.

As shown in Table 1, the moisture content, amounts of organicimpurities, and amounts of the trace metal in the isopropyl alcoholpurified by purification system 10 were significantly reduced.

While the invention has been described in detail with reference tocertain embodiments thereof, it will be understood that modificationsand variations are within the spirit and scope of that which isdescribed and claimed.

What is claimed is:
 1. A method for removing impurities from an organicsolvent, comprising: distilling the organic solvent in a distillationcolumn to obtain a distilled organic solvent; and passing the distilledorganic solvent through an ion exchange filter unit to obtain a purifiedorganic solvent; wherein the ion exchange filter unit comprises ahousing and at least one first ion exchange filter and at least onesecond ion exchange filter in the housing, the at least one first ionexchange filter and the at least one second ion exchange filter are bothnegatively charged ion exchange filters and are connected in series, andthe at least one first ion exchange filter is different from the atleast one second ion exchange filter.
 2. The method of claim 1, whereinthe organic solvent comprises an alcohol.
 3. The method of claim 1,wherein the organic solvent comprises isopropyl alcohol.
 4. The methodof claim 1, wherein the at least one first ion exchange filter comprisesa filtration medium that comprises a polyolefin, a polyamide, afluoropolymer, or a copolymer thereof.
 5. The method of claim 1, whereinthe ion exchange filter unit comprises two to five first ion exchangefilters.
 6. The method of claim 5, wherein the first ion exchangefilters are connected in parallel.
 7. The method of claim 1, wherein theat least one first ion exchange filter is capable of removing at least90 wt% of Fe, Ni, Cr, Zn, or Cu from the organic solvent.
 8. The methodof claim 1, wherein the at least one second ion exchange filtercomprises a filtration medium that comprises a polyolefin, a polyamide,a fluoropolymer, or a copolymer thereof.
 9. The method of claim 1,wherein the filtration medium in the at least one first or second ionexchange filter comprises a polyethylene having sulfonate groups, apolytetrafluoroethylene having sulfonate groups, or a copolymer thereof.10. The method of claim 1, wherein the ion exchange filter unitcomprises two to five second ion exchange filters.
 11. The method ofclaim 10, wherein the second ion exchange filters are connected inparallel.
 12. The method of claim 1, wherein the at least one second ionexchange filter is capable of removing at least 70 wt% of K, Na, or Cafrom the organic solvent.
 13. The method of claim 1, wherein the atleast one second ion exchange filter is disposed downstream of the atleast one first ion exchange filter.
 14. The method of claim 1, furthercomprising passing the organic solvent through a filter unit in fluidcommunication with and between the distillation column and the ionexchange filter unit.
 15. The method of claim 14, wherein the filterunit between the distillation column and the ion exchange filter unitcomprises a housing and at least one particle removal filter in thehousing.
 16. The method of claim 15, wherein the at least one particleremoval filter comprises a filtration medium that comprises apolyolefin, a polyamide, a fluoropolymer, or a copolymer thereof. 17.The method of claim 16, wherein the at least one particle removal filtercomprises a filtration medium that comprises a polytetrafluoroethylene.18. The method of claim 15, wherein the at least one particle removalfilter comprises a filtration medium having an average pore size of fromabout 5 nm to about 50 nm.
 19. The method of claim 1, further comprisingpassing the organic solvent through a filter unit downstream of and influid communication with the ion exchange filter unit.
 20. The method ofclaim 19, wherein the filter unit downstream of the ion exchange filterunit comprises a housing and at least one particle removal filter in thehousing.
 21. The method of claim 20, wherein the at least one particleremoval filter in the filter unit downstream of the ion exchange filterunit comprises a filtration medium that comprises a polyolefin, apolyamide, a fluoropolymer, or a copolymer thereof.
 22. The method ofclaim 21, wherein the at least one particle removal filter in the filterunit downstream of the ion exchange filter unit comprises a filtrationmedium that comprises a polytetrafluoroethylene.
 23. The method of claim20, wherein the at least one particle removal filter in the filter unitdownstream of the ion exchange filter unit comprises a filtration mediumhaving an average pore size of from about 2 nm to about 10 nm.
 24. Themethod of claim 19, further comprising recirculating the organic solventexiting the filter unit downstream of the ion exchange filter unit. 25.The method of claim 24, wherein the recirculating comprises moving theorganic solvent exiting the filter unit downstream of the ion exchangefilter unit to a storage tank and subsequently passing the organicsolvent through the ion exchange filter unit.
 26. The method of claim 1,further comprising moving the purified solvent to a packaging station.27. The method of claim 1, wherein the purified organic solventcomprises metal impurities in a total amount of at most about 200 ppt ofthe purified organic solvent.
 28. A system, comprising: a distillationcolumn; and an ion exchange filter unit downstream of and in fluidcommunication with the distillation column; wherein the ion exchangefilter unit comprises a housing and at least one first ion exchangefilter and at least one second ion exchange filter in the housing, theat least one first ion exchange filter and the at least one second ionexchange filter are both negatively charged ion exchange filters and areconnected in series, and the at least first ion exchange filter isdifferent from the at least one second ion exchange filter.